Tetrabenazine in the treatment of severe pediatric chorea

Treatment of Chorea in Childhood

Chorea is a movement disorder characterized by ongoing random-appearing sequences of discrete involuntary movements or movement fragments. Chorea results from dysfunction of the complex neuronal networks that interconnect the basal ganglia, thalamus, and related frontal lobe cortical areas. The complexity of basal ganglia circuitry and vulnerability of those circuits to injury explains why chorea results from a wide variety of conditions. Because etiology-specific treatments or effective symptomatic treatments are available for causes of chorea, defining the underlying disease is important. The treatment of chorea can be considered in three main categories: (1) terminating or modifying exposure to the causative agent, (2) symptomatic treatment of chorea, and (3) treatment targeting the underlying etiology. Symptomatic treatment decision of chorea should be based on the functional impact on the child caused by chorea itself. There have been no reported randomized, placebo-controlled trials of symptomatic treatment for chorea in childhood. Thus the recommendations are based on clinical experience, case reports, expert opinions, and small comparative studies. Better knowledge of mechanisms underlying childhood chorea will provide more etiology-based treatments in the future.

Management of Pediatric Movement Disorders: Present and Future

Management of movement disorders in children is an evolving field. This article outlines the major categories of treatment options for pediatric movement disorders and general guidelines for their use. We review the evidence for existing therapies, which continue to lack large-scale controlled trials to guide treatment decisions. The field continues to rely on extrapolations from adult studies and lower quality evidence such as case reports and case series to guide treatment guidelines and consensus statements. Developments in new pharmaceuticals for rare diseases have begun to provide hope for those cases in which a genetic diagnosis can be made. Advances in surgical therapies such as deep brain stimulation as well as new modes of treatment such as gene therapy, epigenetic modulation, and stem cell therapy hold promise for improving outcomes in both primary and secondary causes of movement disorders. There is a critical need for larger, multicenter, controlled clinical trials to fully evaluate treatments for pediatric movement disorders.

Tetrabenazine: Spotlight on Drug Review

BACKGROUND

Tetrabenazine (TBZ) is the only US Food and Drug Administration-approved drug for the treatment of chorea related to Huntington's disease and other hyperkinetic disorders. TBZ was first synthesized in 1950, and was then used for the treatment of psychosis. But later its potential in treating hyperkinetic disorders was proved by its ability to block vesicular monoamine transporters 2 and deplete monoamine stores. There is still lack of awareness about the therapeutic potential of this drug.

SUMMARY

TBZ had been approved only for the treatment of chorea, but several clinical studies have been conducted by different research groups and it was concluded that TBZ is effective in various other conditions such as tardive dyskinesia, dystonia, tics, and Tourette's syndrome, thus, highlighting the need for further clinical trials in these conditions.

KEY MESSAGE

The intention of this review is to sum up the information regarding chemistry, mechanism of action, pharmacokinetics, interactions, contraindications, adverse effects, and clinical efficacy of TBZ in diseases other than Huntington's chorea.

Clinical Course of Six Children With GNAO1 Mutations Causing a Severe and Distinctive Movement Disorder

OBJECTIVES

Mutations in GNAO1 have been described in 11 patients to date. Although most of these individuals had epileptic encephalopathy, four patients had a severe movement disorder as the prominent feature. We describe the largest series of patients with de novoGNAO1 mutations who have severe chorea, developmental delay, and hypotonia in the absence of epilepsy.

METHODS

Six patients with recurrent missense mutations in GNAO1 as detected by whole exome sequencing were identified at three institutions. We describe the presentation, clinical course, and response to treatment of these patients.

RESULTS

All six patients exhibited global developmental delay and hypotonia from infancy. Chorea developed by age four years in all but one patient, who developed chorea at 14 years. Treatments with neuroleptics and tetrabenazine were most effective in the baseline management of chorea. The chorea became gradually progressive and marked by episodes of severe, refractory ballismus requiring intensive care unit admissions in four of six patients. Exacerbations indirectly led to the death of two patients.

CONCLUSIONS

Patients with GNAO1 mutations can present with a severe, progressive movement disorder in the absence of epilepsy. Exacerbations may be refractory to treatment and can result in life-threatening secondary complications. Early and aggressive treatment of these exacerbations with direct admission to intensive care units for treatment with anesthetic drips may prevent some secondary complications. However the chorea and ballismus can be refractory to maximum medical therapy.

Pediatric movement disorders

On the basis of some research evidence and consensus, identification of acute opsoclonus, ataxia, or myoclonus should prompt consideration of an underlying neuroblastoma. On the basis of some research evidence and consensus, surgical treatment options should be considered for children with dystonia, including secondary dystonias, such as those related to cerebral palsy, and include intrathecal baclofen pumps and deep brain stimulation. On the basis of some research evidence and clinical experience, tetrabenazine may be effective in treating chorea. On the basis of strong research evidence, although seldom inherently dangerous, tics may be uncomfortable for affected children and interfere with academic achievement and social development. On the basis of some research evidence and clinical experience, topiramate may be an effective treatment for tic disorders.

Spectrofluorimetric determination of tetrabenazine after photochemical derivatization in basic medium

Photochemical derivatization is proposed for the spectrofluorimetric determination of tetrabenazine (TBZ). A central composite design was used to adjust experimental conditions (60 min of UV in a 0.45 mol L(-1) NaOH solution) enabling the improvement of the analyte signal-to-blank ratio of one order of magnitude, when compared to the TBZ original fluorescence. Limit of quantification was 4.7×10(-8) mol L(-1) but the detection power can be improved at least 10 times using solid phase extraction that also allows the separation of the analyte from matrix components, enabling the analysis of biologic fluids. Linear range covered at least three orders of magnitude. The combined uncertainty of the determination (at a 5×10(-6) mol L(-1)) was 16%. Recoveries of TBZ in the analyses of a pharmaceutical formulation were in agreement with the ones obtained using a HPLC method. Recovery in saliva (5×10(-7) mol L(-1) of TBZ) was 90±3% (n=3). The procedure minimizes the use of toxic chemical derivatization reagents and the generation of hazardous waste.

Update on the Non-Huntington's Disease Choreas with Comments on the Current Nomenclature

CHOREA CAN BE CAUSED BY A MULTITUDE OF ETIOLOGIES: neurodegenerative, pharmacological, structural, metabolic, and others. In absence of other apparent causes, exclusion of Huntington's disease is often a first step in the diagnostic process. There are a number of neurodegenerative disorders whose genetic etiology has been identified in the past decade. Molecular diagnosis has enabled genetic identification of disorder subtypes which were previously grouped together, such as the neurodegeneration with brain iron accumulation disorders and the neuroacanthocytosis syndromes, as well as identification of phenotypic outliers for recognized disorders. Correct molecular diagnosis is essential for genetic counseling and, hopefully, ultimately genetic therapies. In addition, there has recently been recognition of other disorders which can mimic neurodegenerative disorders, including paraneoplastic and prion disorders. This article focuses upon recent developments in the field but is not intended to provide an exhaustive review of all causes of chorea, which is available elsewhere. I also discuss the nomenclature of these disorders which has become somewhat unwieldy, but may ultimately be refined by association with the causative gene.

Neuroacanthocytosis

The term "neuroacanthocytosis" describes a heterogeneous group of molecularly-defined disorders which result in progressive neurodegeneration, predominantly of the basal ganglia, and erythrocyte acanthocytosis. The clinical presentation of neuroacanthocytosis syndromes typically involves chorea and dystonia, but a range of other movement disorders may be seen. Psychiatric and cognitive symptoms may be prominent. There can be considerable phenotypic overlap; however, features of inheritance, age of onset, neuroimaging and laboratory findings, in addition to the spectrum of central and peripheral neurological abnormalities and extraneuronal involvement, can help to distinguish the specific syndromes. The two core neuroacanthocytosis syndromes, in which acanthocytosis is a typical, although not invariable finding, are autosomal recessive chorea-acanthocytosis and X-linked McLeod syndrome. Acanthocytes are found in a smaller proportion of patients with Huntington's disease-like 2 and pantothenate kinase-associated neurodegeneration. Additionally, acanthocytosis has been reported in a few patients with other neurological disorders. The causative genes do not appear to be linked by a specific function or pathway, although abnormalities of membrane processing may be implicated. The connection between the erythrocyte membrane abnormality, which results in the characteristic "thorny" protrusions, the vulnerability of the basal ganglia, and the respective genetic mutations, is obscure.

Vascular chorea in adults and children

Chorea may occur as part of the symptomatology of acute stroke; it occasionally also may be delayed or progressive. Patients with vascular-related chorea typically present with an acute or subacute onset of chorea of one side of the body (hemichorea), contralateral to the lesion. Cerebrovascular disease is the most common cause of sporadic chorea. Lesions are most frequently found in the thalamus and lentiform nucleus, and less often in subthalamic nucleus. The differential diagnosis of choreic syndromes relies not so much on differences in the phenomenology of the hyperkinesia but the age at onset, mode of onset, time course, family history, drug use, distribution of chorea in the body, and presence of accompanying neurological findings. Magnetic resonance imaging is preferred to demonstrate the presence of strategic small lesions in regions that are difficult to image with computed tomography, such as the globus pallidus, thalamus, and subthalamic nucleus. Although the prognosis of hemichorea can be benign, the long-term prognosis is not specifically determined by the hemichorea but by the long-term prognosis of stroke patients. Symptomatic treatment with antichoreic drugs may be necessary in the acute phase. Surgery is rarely indicated to treat vascular chorea.

A case of PANDAS treated with tetrabenazine and tonsillectomy

PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections) is a rare clinical syndrome characterized by the presence of tics, Tourette syndrome, obsessive-compulsive disorder, or chorea in the context of an immediately precedent streptococcal infection. In this report, we describe the case of an 11-year-old boy who developed PANDAS with severe choreic movements. The criteria for PANDAS diagnosis were met. Moreover, serum antibrain antibodies were present. The patient was initially treated with tetrabenazine 12.5 mg twice daily with remission of the neurological symptoms. Subsequently, the patient underwent tonsillectomy and has been asymptomatic since, with antistreptolysin O titer levels in range.

[Treatment of childhood dystonia]

Dystonia is not uncommon in childhood, but is clinically very heterogeneous. Therefore, introduction and follow-up of the treatment of dystonia in children are often a challenge for the physicians. Progresses in functional neurosurgery have open new fields in the treatment of dystonia in children, but it should be managed by a multidisciplinary team. This paper reviews the various therapeutic options available for childhood-onset dystonia, with a specific attention to dosage and side effects of the drugs regarding pediatric population according to the data of the literature. The rational strategy for therapeutic management of the various types of childhood dystonia is discussed.

Tetrabenazine

BACKGROUND

Tetrabenazine (TBZ) depletes presynaptic dopamine in the CNS. It has been found to be beneficial in hyperkinetic movement disorders without carrying the extrapyramidal side effects that are characteristic of neuroleptics.

OBJECTIVE

To summarize current knowledge on the use of TBZ and draw conclusions about its efficacy and safety.

METHODS

PubMed literature searches using the term 'tetrabenazine' were carried out for the period prior to May 2009. Additional relevant studies referenced by these publications were included.

CONCLUSIONS

Both short- and long-term studies have consistently yielded favorable results for the use of TBZ in the treatment of hyperkinetic movement in terms of efficacy and safety. TBZ is most effective in reducing chorea (including Huntington's disease associated chorea), tic associated with Tourette's syndrome and tardive dyskinesias. Furthermore, TBZ might also have potential for use in other hyperkinetic disorders (e.g., myoclonus and dystonia), for which future clinical trials are needed.

Tourette's syndrome and role of tetrabenazine: review and personal experience

Gilles de la Tourette's syndrome (Tourette's syndrome; TS) is an inherited tic disorder commonly associated with other neurobehavioural conditions such as attention-deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD). While the clinical presentation of TS and other features of this disorder have been well characterized, the genetic and neurobiological basis of the disease remains incompletely elucidated. The suggestion of a central role of dopamine in the aetiology of TS has been made on the basis of experimental studies, evidence from neuroimaging studies and the therapeutic response patients with TS have to agents that antagonize or interfere with putative dopaminergic pathways. Tetrabenazine is such an agent; it depletes presynaptic dopamine and serotonin stores and blocks postsynaptic dopamine receptors. In clinical studies, tetrabenazine has been found to be effective in a wide range of hyperkinetic movement disorders, including small numbers (<50) of patients with TS in some studies. Results of a retrospective chart review enrolling only patients with TS (n = 77; mean age approximately 15 years) showed that 2 years' treatment with tetrabenazine resulted in an improvement in functioning and TS-related symptoms in over 80% of patients, findings that suggest that treatment with tetrabenazine may have long-term benefits. The authors' experience with 120 heavily co-medicated patients with TS confirms these findings. Long-term (mean 19 months) tetrabenazine treatment resulted in a Clinical Global Impressions of Change scale rating of 'improved' in 76% of patients. Such findings are promising and suggest that tetrabenazine may be suitable as add-on therapy in patients for whom additional suppression of tics is required.

Short-term effects of tetrabenazine on chorea associated with Huntington's disease

We sought to assess the short-term clinical effects of tetrabenazine (TBZ) on choreic movements in Huntington's disease patients. A total of 10 patients on stable doses of TBZ were enrolled in this observational study. Patients took their evening dose of TBZ and presented the next day to the Baylor College of Medicine Movement Disorders Clinic without taking the usual morning dose. They were assessed using the Unified Huntington's Disease Rating Scale (UHDRS) motor assessment and Beck Depression Inventory. The usual morning dose of TBZ was then administered and patients were followed with serial UHDRS motor examinations approximately every 2 hours until choreic movements subsided and then returned. TBZ decreased the UHDRS chorea score on average 42.4% +/- 17.8%. The duration of effect varied from a minimum of 3.2 hours to a maximum of 8.1 hours (mean = 5.4 +/- 1.3). No patient experienced an adverse event related to TBZ or its withdrawal. During short-term follow-up after a single dose, TBZ improves chorea for approximately 5 hours.

Tetrabenazine therapy of pediatric hyperkinetic movement disorders

Tetrabenazine (TBZ), a presynaptic dopamine depletor and postsynaptic dopamine receptor blocker, is widely used for the treatment of hyperkinetic movement disorders in adults. However, reports of its use in children are limited. We review the efficacy and tolerability of TBZ therapy in 31 children with hyperkinetic movement disorders refractory to other medications. TBZ was effective in reducing the severity of movement disorders resistant to treatment with other medicines. When compared to adult patients, pediatric patients required higher doses. Side effects were similar to the adult population; however, children had a lower incidence of drug-induced Parkinsonism.

Seminar on choreas

Chorea is one of the major types of involuntary movement disorders originating from dysfunctional neuronal networks interconnecting the basal ganglia and frontal cortical motor areas. The syndrome is characterised by a continuous flow of random, brief, involuntary muscle contractions and can result from a wide variety of causes. Diagnostic work-up can be straightforward in patients with a positive family history of Huntington's disease or acute-onset hemichorea in patients with lacunar stroke, but it can be a challenging and complex task in rare autoimmune or genetic choreas. Principles of management focus on establishing an aetiological classification and, if possible, removal of the cause. Preventive strategies may be possible in Huntington's disease where genetic counselling plays a major part. In this review we summarise the current understanding of the neuroanatomy and pathophysiology of chorea, its major aetiological classes, and principles of diagnostic work-up and management.

Tetrabenazine in the treatment of hyperkinetic movement disorders

Tetrabenazine, a dopamine-depleting agent first synthesized half a century ago, was initially developed for the treatment of schizophrenia. Although psychotic disorders have since been treated more successfully with other neuroleptic medications, many studies have shown this drug to be effective in the treatment of hyperkinetic movement disorders (hyperkinesias). Hyperkinesias are neurologic disorders characterized by abnormal involuntary movements such as chorea associated with Huntington's disease, tics in Tourette's syndrome and stereotypies in tardive dyskinesia. Recently, clinical trials investigating tetrabenazine for the treatment of chorea associated with Huntington's disease found the drug to be safe and efficacious, making approval by the US Food and Drug Administration for this indication a distinct possibility.

Movement disorder emergencies

Movement disorders may present acutely, and failure to recognize and exclude important differential diagnoses can result in significant morbidity or mortality. Unfortunately, much of the literature pertaining to this topic is scattered and not easily accessible. This review aims to address this deficit. Movement disorder emergencies are discussed according to their most likely mode of presentation. Diagnostic considerations and early management principles are reviewed, along with appropriate pathophysiology where relevant.

Chorea and related disorders

Chorea refers to irregular, flowing, non-stereotyped, random, involuntary movements that often possess a writhing quality referred to as choreoathetosis. When mild, chorea can be difficult to differentiate from restlessness. When chorea is proximal and of large amplitude, it is called ballism. Chorea is usually worsened by anxiety and stress and subsides during sleep. Most patients attempt to disguise chorea by incorporating it into a purposeful activity. Whereas ballism is most often encountered as hemiballism due to contralateral structural lesions of the subthalamic nucleus and/or its afferent or efferent projections, chorea may be the expression of a wide range of disorders, including metabolic, infectious, inflammatory, vascular, and neurodegenerative, as well as drug induced syndromes. In clinical practice, Sydenham's chorea is the most common form of childhood chorea, whereas Huntington's disease and drug induced chorea account for the majority of adult onset cases. The aim of this review is to provide an up to date discussion of this disorder, as well as a practical approach to its management.

Metoclopramide-induced tardive dyskinesia in an infant

We describe a 1-year-old girl who developed orofaciolingual stereotypy at age 2 months after a 17-day treatment with metoclopramide for gastroesophageal reflux. The stereotypy, documented by sequential videos, persisted for at least 9 months after the drug was discontinued. This patient represents the first documented case of tardive dyskinesia in an infant. We also review previous reports of tardive dyskinesia in children.

Movement disorder emergencies in the perioperative period

Movement disorder emergencies are uncommon in the perioperative period; however, when they occur, then carry significant morbidity. By paying attention to the phenomenology of the movement disorder, the effects of medications administered in the operating room, and unusual sequelae of surgery, neurologists can have a positive impact on the outcome of these patients.